Graphene modified Nd/TiO2 photocatalyst for methyl orange degradation under visible light irradiation

A novel nanoscale GR–Nd/TiO₂ composite photocatalyst was synthesized by the hydrothermal method. Its crystal structure, surface morphology, chemical composition and optical properties were studied using XRD, TEM, and XPS, DRS and PL spectroscopy. It was found that graphene and neodymium modification shifts the absorption edge of TiO₂ to visible-light region. The results of photoluminescence (PL) emission spectra show that GR–Nd/TiO₂ composites possess better charge separation capability than do Nd/TiO₂ and pure TiO₂. The photocatalytic activity of prepared samples was investigated by degradation of methyl orange (MO) dye under visible light irradiation. The results show that the GR–Nd/TiO₂ composite can effectively photodegrade MO, showing an impressive photocatalytic activity enhancement over that of pure TiO₂. The enhanced photocatalytic activity of the composite catalyst might be attributed to the large adsorptivity of dyes, extended light absorption range and efficient charge separation due to Nd doping and graphene incorporation.     

Y2O3-Bi2O3可见光催化降解甲基橙

采用固相合成法制备了Y<,2>O<,3>-Bi<,2>O<,3>复合可见光催化剂,用XRD、DRS对复合催化剂进行了表征.以甲基橙为模拟废水,在日光色镝灯光照下,研究了废水浓度、催化剂投加量、温度、pH等对Y<,2>O<,3>-Bi<,2>O<,3>光催化活性的影响.实验结果表明:在甲基橙质量浓度为20 mg/L、Y<...     

ZnO assisted photocatalytic degradation of acridine orange in aqueous solution using visible irradiation

A detailed investigation of photocatalytic degradation of the dye, acridine orange, has been carried out in aqueous heterogeneous medium containing ZnO as photocatalyst in a batch reactor. Visible light in the absence of ZnO has negligible effect on degradation. The disappearance of the dye, monitored spectrophotometrically, follows approximately pseudo-first order kinetics according to the Langmuir–Hinshelwood model. The total degradation of dye was tested using the chemical oxygen demand (COD) method. The addition of an optimal amount of hydrogen peroxide and potassium persulphate increases the degradation rate while NaCl and Na₂CO₃ decreases. The effect of addition of cationic and anionic surfactants has also been investigated. Bubbling of nitrogen in the reaction solution decreases the reaction rate. ZnO has been found experimentally to be a highly efficient photocatalyst for the degradation of acridine orange dye and hence there is a great potential in the treatment of organic pollutants such as dyes.     

TiO2混晶负载磷钨酸借自然光照对甲基橙的脱色性能研究

研究了以TiO2混晶负载磷钨酸为光催化剂,在光照条件下模拟染料废水甲基橙溶液的光催化脱色性能。实验结果表明:催化剂的投入量,甲基橙的初始浓度,光照时间是影响甲基橙溶液脱色率的重要因素。当H3PW12O40/TiO2催化剂用量为1.5 g/L,甲基橙的初始浓度为10 mg/L,光照时间为2.5 h时,甲基橙溶液的脱色率可达97.9%。     

Fabrication of CdS and CuWO4 modified TiO2 nanoparticles and its photocatalytic activity under visible light irradiation

CdS and CuWO₄ modified TiO₂ nanoparticles (CdS–CuWO₄-TiO₂) were prepared by the chemical impregnation method. The as-prepared nanoparticles were characterized using UV–visible-diffuse reflectance spectroscopy (UV–vis-DRS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and B.E.T. surface area analysis techniques. The photocatalytic activity was evaluated based on the degradation of a dye (eosin-Y) and inactivation of a bacterium (Pseudomonas aeruginosa). The results revealed that CdS–CuWO₄-TiO₂ showed high photocatalytic activity over CdS-TiO₂, CuWO₄-TiO₂ and TiO₂. Moreover the reusability and stability of the photocatalyst for the degradation of eosin-Y was also studied.     

TiO_2可见光催化的研究进展

综述了近年来国内外研究TiO2可见光催化反应的进展,如金属或非金属掺杂、染料光敏化、与其它半导体复合、与H2O2复合等,阐述了TiO2可见光催化的反应机制,指出了TiO2可见光催化存在的主要问题、发展前景及今后的研究方向。     

可见光响应的非金属离子掺杂二氧化钛的研究进展

TiO_2的宽禁带宽度[Eg=(3.0～3.2)eV]限制了其光催化特性的实际应用,非金属元素掺杂为提高TiO_2在可见光光催化活性提供了契机。介绍了非金属元素(氮、碳、硫、氟和硼)掺杂TiO_2的制备方法和可见光催化活性的研究进展,分析非金属元素对TiO_2可见光催化活性的诱导机理。制备工艺影响掺杂元素的化学态和含量,决定掺杂元素在TiO_2晶体微观状态。掺杂元素在TiO_2晶体微观状态与TiO_2可见光催化活性具有相关性,对未来的研究方向进行了展望。     

Photocatalytic degradation of dyestuff wastewater under visible light irradiation using micron‐sized mixed crystal TiO2 powders

A phase transformation of micron‐sized TiO₂ powder from anatase to rutile was attempted by heat‐treatment in order to generate a new mixed crystal TiO₂ with high associated photocatalytic activity. Heat‐treated micron‐sized TiO₂ powders at different transition stages were characterized by X‐ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT‐IR) and transmission electron microscopy (TEM) methods. The tests of photocatalytic activity of the heat‐treated micron‐sized TiO₂ powders were conducted by the photocatalytic degradation of Rhodamine B and Acid Red B under visible light irradiation. The results indicate that mixed crystal TiO₂ photocatalyst heat‐treated at 400 °C for 60 min shows the highest photocatalytic activity. It can effectively decompose the Rhodamine B and Acid Red B in aqueous solution after 6 h visible light irradiation. A remarkable improvement in photocatalytic activity of TiO₂ is caused by the formation of combined rutile–anatase phases and separation of photogenerated electron–hole pairs. Copyright © 2007 Society of Chemical Industry     

Fe-Sr2Bi2O5光催化降解低密度聚乙烯膜

采用共沉淀法合成的新型光催化剂(Fe-Sr₂Bi₂O₅)与低密度聚乙烯(LDPE)通过熔融共混制备了一种新型光催化降解复合膜(Fe-Sr₂Bi₂O₅/PE)。通过力学性能、接触角、傅里叶变换红外光谱(FT-IR)和场发射扫描电镜(FESEM)等表征手段研究了该催化剂在室温条件下固相光催化降解LDPE复合膜的性能变化。结果表明:Fe-Sr₂Bi₂O₅在紫外光和可见光条件下对LDPE均具有较好的光催化降解能力,其中,紫外灯照射10 d后,Fe-Sr₂Bi₂O₅/PE复合膜断裂伸长保留率低于5%,拉伸强度保留率低于40%,接触角降低22.52°,已完全脆化;同时,LDPE复合膜中出现明显的羰基等降解特征吸收峰和降解孔洞;与Sr₂Bi₂O₅和TiO₂相比,Fe-Sr₂Bi₂O₅对LDPE具有更好的降解效果。综上所述,在紫外光和可见光条件下,Fe-Sr₂Bi₂O₅对LDPE具有明显的光催化降解作用,为未来光催化降解聚乙烯(PE)提供了一定的新依据。     

Graphene-ZnO nanocomposite for highly efficient photocatalytic degradation of methyl orange dye under solar light irradiation

A facile synthesis of graphene oxide-zinc oxide nanocomposite (GO-ZnO) was performed by using wet chemical method of graphene oxide and zinc acetate precursors. The nanocomposite was characterized and intercalated with Raman spectroscopy, FE-SEM, TEM, SAED and EDAX. The crystalline nature was studied from P-XRD, and surface area of the sample was analyzed by BET. The chemical composition was explained in the light of XPS phenomenon. The photo electron-excitation (PL) studies were conducted for understanding the photocatalytic mechanism, and photocatalytic degradation of methyl orange was studied by using UV-VIS spectrophotometer. We investigated the photocatalytic activity involving GO-ZnO nanocomposite besides checking the re-stability of the composite. Significant high-performance photocatalytic activity of GO-ZnO nanocomposite was exhibited on methyl orange degradation under solar light.     

Plasmonic enhancement of photocatalytic decomposition of methyl orange under visible light

By integrating strongly plasmonic Au nanoparticles with strongly catalytic TiO₂, we observe enhanced photocatalytic decomposition of methyl orange under visible illumination. Irradiating Au nanoparticles at their plasmon resonance frequency creates intense electric fields, which can be used to increase electron–hole pair generation rate in semiconductors. As a result, the photocatalytic activity of large bandgap semiconductors, like TiO₂, can be extended into the visible region of the electromagnetic spectrum. Here, we report a 9-fold improvement in the photocatalytic decomposition rate of methyl orange driven by a photocatalyst consisting of strongly plasmonic Au nanoparticles deposited on top of strongly catalytic TiO₂. Finite-difference time-domain (FDTD) simulations indicate that the improvement in photocatalytic activity in the visible range can be attributed to the electric field enhancement near the metal nanoparticles. The intense local fields produced by the surface plasmons couple light efficiently to the surface of the TiO₂. This enhancement mechanism is particularly effective because of TiO₂’s short exciton diffusion length, which would otherwise limit its photocatalytic efficiency. Our electromagnetic simulations of this process suggest that enhancement factors many times larger than this are possible if this mechanism can be optimized.     

Efficient hydrogen production by photocatalytic water-splitting using Pt-doped TiO2 hollow spheres under visible light

Pt doped TiO₂ hollow spheres (Pt/HS-TiO₂) are prepared by a sol–gel method and characterized by XRD, SEM, TEM and UV-visible absorption spectra. In addition, Pt/HS-TiO₂ is employed as the catalyst for photocatalytic hydrogen production from water splitting under visible light irradiation. The results show that Pt/HS-TiO₂ with hollow sphere structure presents excellent photocatalytic hydrogen evolution performance. The hydrogen generation rate can reach more than 1023.71 μmol h⁻¹ g⁻¹ at room temperature and no obvious deactivation is observed after 30 h irradiation. Furthermore, the reactively of Pt/HS-TiO₂ could be reproduced in the repeated cycle. Therefore, Pt/HS-TiO₂ is a promising photocatalyst to efficiently generate hydrogen under visible-light irradiation at room temperature.     

Multiple-metal-doped Fe3O4@Fe2O3 nanoparticles with enhanced photocatalytic performance for methyl orange degradation under UV/solar light irradiation

Waelz slag, which is a Fe-bearing hazardous waste, was applied as the raw material in the synthesis of M-Fe₃O₄@Fe₂O₃ (M = Al, Zn, Cu, and Mn) nanoparticles, which are potential photocatalysts. Through acidolysis, 97.23% of Fe and most of the valuable metals were extracted from this slag. Using sol-gel processes, designed Fe₃O₄@Fe₂O₃ nanoparticles doped with multiple elements were systematically synthesised and characterised using X-ray diffraction, field emission scanning electron microscopy, electron diffraction spectroscopy, transmission electron microscopy, and Brunauer–Emmett–Teller analysis. The photocatalytic activities of the synthesised particles and undoped Fe₂O₃ nanoparticles were compared through photocatalytic methyl orange degradation experiments under UV and simulated solar light. The results indicated that all of the slag-derived nanoparticles gave improved photocatalytic performances compared to the undoped sample, and the M-Fe₃O₄@Fe₂O₃ (M = Al, Zn, and Cu) sample exhibited the best photocatalytic activity. The enhancement can be attributed to grain refinement, doping, and the formation of a typical Fe₃O₄@Fe₂O₃ core-shell structure.     

Silica induced oxygen vacancies in supported mixed-phase TiO2 for photocatalytic degradation of phenol under visible light irradiation

Phenol degradation with TiO₂ has attracted a great deal of interest in recent years. However, its low efficiency under solar radiation and difficulty of recovery limit the potential use. Here we report a novel “silica support inducing oxygen vacancies” strategy to prepare visible-light-active TiO₂ with mixed-phase, which show excellent photocatalytic performance for phenol degradation under visible light. Hydroxyl and superoxide radicals were the main oxidative species responsible for the degradation of phenol. Our work demonstrates that coupling with oxygen vacancy creation and silica nanosheets (SNSs) immobilization for TiO₂ is a new approach to obtained efficient visible-light photocatalysts for practical application.     

TiO2纳米管阵列电催化降解甲基橙

采用阳极氧化法制备了TiO2纳米管阵列电极,通过考察其对模拟染料废水甲基橙(MO)的光催化降解效率来优化制备条件。研究了TiO2纳米管阵列电极电催化降解MO的活性及其影响因素,并考察了MO降解反应动力学。结果表明,MO溶液pH、电解槽压、支持电解质浓度等是TiO2纳米管阵列电极催化效率的重要影响因素。TiO2纳米管阵列电催化降解MO的反应遵守一级反应动力学规律,与TiO2纳米管阵列光催化降解MO的行为一致,且表观反应速率常数不随MO溶液浓度不同而发生改变。     

Aerosol processing of Ag/TiO2 composite nanoparticles for enhanced photocatalytic water treatment under UV and visible light irradiation

In this study, we investigated the effect of Ag addition on the photocatalytic reactivity of TiO₂ nanoparticles (NPs). Controlled amounts of Ag were incorporated in TiO₂ NPs using aerosol spray pyrolysis and subsequent calcination. Ag/TiO₂ composite NPs containing different amounts of Ag (e.g., 0, 0.5, 1, 2, and 5 wt%) were successfully fabricated. The photodegradation performances of the as-prepared Ag/TiO₂ composite NPs were tested using methylene blue (MB) solution under UV and visible light irradiation. Upon increasing the Ag content to 1 wt%, the resulting Ag/TiO₂ composite NPs exhibited increased photocatalytic reactivity due to lowered bandgap energy, which promoted both charge generation and separation. However, when the Ag content exceeded 1 wt%, the photocatalytic reactivity of the resulting Ag/TiO₂ composite NPs was considerably deteriorated due to the masking effect of the excess Ag on the reactive sites of TiO₂. Hence, the incorporation of an optimized amount of Ag in the TiO₂ matrix promotes the photocatalytic reactivity of Ag/TiO₂ composite NPs by controlling their bandgap energy and charge generation and separation processes. These results could lead to the development of photodegradation active substances for water treatment in organic solutions.     

Photocatalytic performance of plasma sprayed Pt-modified TiO2 coatings under visible light irradiation

Plasma sprayed Pt/TiO₂ coatings were prepared by Atmospheric Plasma Spraying process. As-sprayed coatings were characterized by TEM, XRD and XPS. The photocatalytic performance was evaluated through the photo mineralization of methylene blue. All the Pt modified titanium dioxide coatings show significant absorption in the visible light range, while the pure titania coating reflects almost all the visible light. The photocatalytic efficiencies of as-sprayed pure TiO₂ coating and Pt/TiO₂ coatings are almost same under the irradiation of visible light. However, the efficiencies of all Pt/TiO₂ coating are greatly improved comparing with that of pure TiO₂ coating by applying 15 V external bias under the irradiation of visible light.     

Photocatalytic degradation of phenols in aqueous solution under irradiation of 254 and 185 nm UV light

The photocatalytic decomposition and mineralization of 4-chlorophenol (4-CP), hydroquinone and 4-nitrophenol (4-NP) in aqueous solution were investigated using two kinds of low-pressure mercury lamps: one was UV (ultraviolet) lamp emitting at 254 nm and the other was VUV (vacuum ultraviolet) lamp emitting at both 254 and 185 nm. VUV irradiation led to the most efficient degradation of the organics. Different mechanisms of photocatalysis and photolysis under VUV irradiation were observed. The degradation rate was subjected to the molecular structures of the substrates. 4-CP was easy to be decomposed, while hydroquinone was easy to be mineralized. However 4-NP was difficult to be decomposed or mineralized. VUV was efficient for decomposition of refractory compounds, such as nitrophenols, and the catalyst was efficient for TOC removal.     

Efficient degradation of 4-nitrophenol by using functionalized porphyrin-TiO2 photocatalysts under visible irradiation

The effect of a series of carboxylic acids (C₂–C₈), as solvents for the preparation by flame spray pyrolysis of LaCoO₃ catalyst for the flameless combustion of methane, has been investigated. Acetic acid showed to be unsatisfactory from several points of view: low phase purity of the catalyst, higher amount of unburnt carbonaceous residua, lower catalytic activity and low thermal stability. By increasing the carbon chain length of the solvent, the consequent increase of flame temperature led to an increase of crystal phase purity and of particle size and to a decrease of specific surface area of the catalyst. Catalytic activity showed only marginally affected by the last parameter, phase purity seeming more important. Thermal resistance showed directly related to flame temperature, i.e. to the combustion enthalpy of the solvent, but a relatively high amount of residual organic matter can negatively affect this property.     

WO_3/BiOBr复合催化剂的制备及可见光催化降解甲基橙

以Bi(NO_3)5·5H_2O、Na Br、H_2WO_4为原料,采用一步水热合成法合成不同n(W)∶n(Br)的WO_3/BiOBr复合催化剂,并通过SEM和TEM对催化剂进行表征分析。以甲基橙为探针污染物,考察前驱液pH、水热温度、水热时间和n(W)∶n(Br)对WO_3/BiOBr复合催化剂活性的影响。结果表明,在pH为10.2、100℃水热时间6 h合成n(W)∶n(Br)为0.02的WO_3/BiOBr复合催化剂活性最好,光照120 min后,对目标污染物的降解率达99.39%,较BiOBr催化剂(合成条件为原始pH值,100℃水热反应6 h)提高了30.85%。采用水热合成法制备的WO_3/BiOBr复合催化剂具有良好的可见光活性。